1. Field Of The Invention
This invention relates to electric regeneration apparatus for driving a load, and more particularly to a power-supply system having two electric motors and two banks of batteries for driving an electric vehicle. 2. Description Of The Prior Art
Considerable interest has been displayed over the years in designing an electric car which can be economically and reliably operated by the average consumer. Most known systems have the disadvantage that their operational range is limited due to the requirement of periodically recharging the batteries. By continually charging and discharging a battery, the battery life is reduced and its ability to be recharged effectively also suffers. Thus, by alternating a battery between a discharge and charge state, the batteries must be replaced periodically, thus increasing the cost of operating an electrical vehicle.
An additional problem with known electrical vehicles is that they are incapable of operating over long distances. By constantly alternating between a charge and a discharge state, each battery quickly is reduced to a condition where it cannot provide sufficient power to drive the vehicle. Solutions have been proposed to recharge the batteries while the vehicle is in operation. Such solutions include the provision of electric generators attached to the vehicle wheels so that excess drive force (for instance when the vehicle is moving downhill) may be converted into recharging power to recharge the batteries. However, such solutions are dependent upon the terrain over which the vehicle must operate and hence do not provide a reliable and predictable range for the electric vehicle.
At present, research is being performed to create new types of batteries in order to overcome inherent problems that presently exist in providing an electric power system for vehicles. However, to applicant's knowledge, there is no satisfactory system which allows an electrically operated vehicle to perform for substantially long periods of time over long distances.
Referring to FIG. 1, the charge/discharge method of operating known electrical vehicles is shown. In FIG. 1 it can be seen that the periods of discharge are equal in time to the periods of recharge. Such a charge/discharge method is known in the art as "deep cycling". Whenever the period of battery recharge is less than or equal to the period of battery discharge, such deep cycling occurs and is disadvantageous to the performance and life of the battery. It is known in the art that batteries are discharged faster than they can be recharged. Thus, each recharge cycle of FIG. 1 is incapable of returning the battery to its charge condition prior to the discharge phase. Thus, at the completion of each recharge phase, the charge state of the battery is progressively reduced. Such deep cycling rapidly reduces the life of the battery requiring costly replacement. An additional disadvantage of deep cycling is that the batteries are quickly reduced to a state where they are incapable of providing sufficient power to the vehicle and must be recharged. Thus, a major design factor is the requirement of most electrical vehicles to be recharged after relatively short periods of operation.
Many devices are known for powering electrical vehicles which attempt to overcome some of the problems described above. For example, U.S. Pat. No. 4,348,628 to Loucks discloses an electric motor alternating power supply for vehicles in which two batteries are provided which alternately drive the vehicle. A voltage sensor senses the charge condition of each battery and switches between the batteries depending upon their charge states. For recharging his batteries, Loucks provides alternators which presumably are powered by the vehicle drive shaft. One alternator is associated with each battery. However, Loucks' batteries are still subject to the deep cycling phenomenon depicted in FIG. 1. Thus, each battery is incapable of being recharged for a period of time greater than its being discharged. In addition, by coupling the alternators to the drive shaft, Loucks' recharging system is dependent upon the terrain over which the vehicle is operated. Plus, by switching between the batteries with a voltage sensor, a battery may be discharged after it has had an insufficient period of recharging so that permanent damage to the battery may be inflicted.
U.S. Pat. No. 4,297,590 to Vail discloses a power supply system in which three banks of batteries are provided to drive the load. Vail connects two of the battery banks to the load while the third battery bank is being recharged. Thus, for each battery, the period of discharge is longer than the period of recharge, thus reducing battery life and effectiveness. Vail attempts to minimize the deleterious effects of deep cycling by switching between the three battery banks after a given period of time. However, each battery will still discharge for a period of time longer than it will recharge.
U.S. Pat. No. 4,360,766 to Bogardus, Jr. discloses a multi-battery power supply for DC motors in which a plurality of batteries may be connected to the driving load depending upon need. Thus, batteries are connected to the load as required. However, a period of heavy demand on the batteries will require that all of them be connected in series, permitting none of them to be recharged for extended periods of time. Such a load-demand system places the battery life in jeopardy depending solely upon the power demanded by the load.
U.S. Pat. No. 3,845,835 to Petit discloses an electric power plant for an electric vehicle having two sets of batteries which are alternately charged and discharged. Switching between batteries is performed by a timer switch to insure that the batteries will not be drained if a heavy load condition exist (for example driving uphill) for a long period of time. Petit recharges his batteries with alternators which are connected to a vehicle axle. Therefore, the recharging energy available is restricted by the energy consumed by the vehicle during operation. The apparatus according to Petit is still subject to the deep cycle phenomenon discussed with reference to FIG. 1. Thus, a vehicle according to Petit will tend to require recharging after relatively short periods of operation, and the batteries will have to be replaced when they are no longer capable of being recharged to an operable state.
As can be appreciated from the above discussion, no known systems are designed to avoid the deep cycle phenomenon and to recharge the batteries with a recharging power which is not subject to the driving power demands of the vehicle or the terrain over which the vehicle operates.